TM and Tm go into idle mode if they receive a packet after boot
time. When tebooting the device over the packet link, the packet
master would be (rapidly) polling the device for additional data and
so the device would invariably receive a packet during bootup and go
into idle mode again.

Delay the reboot by a second to give the controller time to disable
the master end of the packet link.

Before being written the first time, ao_config will get set to 0xff
when the config storage is read. This leaves the tail of the callsign
filled with invalid bytes. Zero the whole thing before loading the
default callsign to make sure any extra bytes are set correctly.